JP7669261B2 - Organic Piezoelectric Film - Google Patents

Description

The present invention relates to an organic piezoelectric film.

2. Description of the Related Art Conventionally, various organic piezoelectric films and inorganic dielectric films are known as films or membranes having piezoelectricity.
Among them, organic piezoelectric films have the advantage of being flexible, unlike inorganic dielectric films, and therefore can be used in a variety of applications.
For example, Patent Document 1 discloses a polarized vinylidene fluoride/tetrafluoroethylene copolymer film for use in a touch panel or for detecting touch pressure as a piezoelectric film.

In recent years, an increasing number of electronic devices are being equipped with touch panels instead of mechanical buttons as input members due to their superior operability. However, mechanical buttons have the disadvantage that users cannot get the same operational feel as when they move a button, whereas touch panels have the disadvantage that users cannot get the same operational feel as when they move a button.
In order to overcome such disadvantages, a touch panel equipped with a flexible piezoelectric actuator that provides tactile feedback to a user who operates the touch panel has been proposed (for example, Patent Document 2). Such devices that use technology for providing tactile feedback to a user who operates the touch panel are generally referred to as haptic devices.

On the other hand, mobile electronic devices such as smartphones and tablets are equipped with secondary batteries because they are carried around by the user. In order to reduce the frequency of charging, a vibration power generation device using a piezoelectric element that can be used in such electronic devices has been proposed (Patent Document 3).

Piezoelectric film is a piezoelectric element that is easy to process and form into a thin film over a large area, and compared to conventional ceramic piezoelectric elements, it is possible to create dynamic pressure sensors with a large area and high voltage sensitivity. For example, it can be used as a pressure sensor to detect the load applied to elastic supports such as beds, mats, and sheets, and determine the presence or absence of people, animals, objects, etc.

2. Description of the Related Art In recent years, research into flexible displays using flexible substrates such as plastics has progressed.
As an example of such a substrate for a flexible display, Patent Document 4 discloses a flexible display substrate in which a gas barrier layer and a transparent conductive layer are laminated on a transparent plastic film.
Flexible displays have advantages over conventional displays using glass substrates in terms of light weight, thinness, flexibility, etc., and therefore can be installed on curved surfaces such as cylinders. Furthermore, they can be rolled up for storage, so portability is not compromised even with a large screen. Due to these advantages, flexible displays have been attracting attention for use in, for example, advertisement displays and display devices such as PDAs (personal digital assistants).
When such a flexible display is used as an image display device and sound generating device that reproduces sound along with images, such as a television receiver, a speaker, which is an acoustic device for generating sound, is required.
Here, conventional speaker shapes are generally a funnel-shaped so-called cone type and a spherical dome type. However, if these speakers are built into the flexible display, there is a risk that the advantages of the flexible display, such as light weight and flexibility, will be lost. On the other hand, if the speaker is attached externally, there is a risk that disadvantages such as portability will be reduced, installation on a curved wall will be difficult, and the aesthetic appearance will be impaired will occur.
In this context, for example, Patent Document 5 discloses the use of a sheet-like flexible piezoelectric film as a speaker that can be integrated into a flexible display without compromising its light weight and flexibility.

JP 2011-222679 A JP 2003-288158 A JP 2011-97661 A JP 2000-338901 A JP 2008-294493 A

In recent years, there has been a demand for larger touch panels, and therefore, in a touch panel capable of detecting touch pressure, it is desirable for the piezoelectric film used for detecting touch pressure to also have a large screen.
However, when conventional piezoelectric films are used in such large-screen touch panels, the in-plane variation in piezoelectricity is not sufficiently small.
Specifically, if the in-plane variation in piezoelectricity of an organic piezoelectric film used in a touch panel capable of detecting touch pressure (especially a large-screen touch panel) is not small enough, even with the same pressure, the electrical signal generated will vary depending on the touch position, resulting in the device determining that the pressure is different and causing a malfunction.

Furthermore, when conventional piezoelectric films are used in haptic devices, the in-plane variation in piezoelectricity is not sufficiently small.
Specifically, if the in-plane variation in piezoelectricity of the organic piezoelectric film used in a haptic device is not small enough, variation will occur in the tactile feedback, preventing a stable operating feel, leading to operational errors and malfunctions of the device.

Furthermore, when conventional piezoelectric films are used in vibration power generation devices, the in-plane variation in piezoelectricity is not sufficiently small.
Specifically, if the in-plane variation in piezoelectricity of the organic piezoelectric film used in the vibration power generation device is not small enough, a constant and stable amount of power generation cannot be obtained even if the amount of vibration is the same.

In addition, if the in-plane variation in piezoelectricity of the organic piezoelectric film used in a pressure sensor (especially a large-area pressure sensor) is not small enough, even with the same pressure, the electrical signal generated will vary depending on the position where the pressure is applied, resulting in unstable sensing.

In addition, if the in-plane variation in piezoelectricity of the organic piezoelectric film used in flat speakers (especially large-area flat speakers) is not small enough, the sound generated will vary depending on the location on the surface, resulting in a problem of poor sound quality.

Therefore, the objective of the present invention is to provide an organic piezoelectric film with particularly small in-plane variation in piezoelectricity.

As a result of extensive investigation, the present inventors have found that
The inventors have found that the above-mentioned problems can be solved by an organic piezoelectric film having a coefficient of variation of the piezoelectric constant _d33 of 50% or less, and have thus completed the present invention.

The present invention includes the following aspects:

Item 1.
An organic piezoelectric film having a coefficient of variation of piezoelectric constant _d33 of 2.0 or less.
Item 2.
Item 2. An organic piezoelectric film according to item 1, having a piezoelectric constant d ₃₃ in the range of 0.5 to 30 pC/N.
2. The organic piezoelectric film according to item 1, wherein the piezoelectric constant d ₃₃ is within the range of 0.5 to less than 2.0 pC/N.
Item 4.
2. An organic piezoelectric film according to item 1, wherein the piezoelectric constant d ₃₃ is in the range of 2.0 to less than 4.0 pC/N, and the variation coefficient thereof is 1.0 or less.
Item 5.
2. An organic piezoelectric film according to item 1, wherein the piezoelectric constant d ₃₃ is in the range of 4.0 to less than 6.0 pC/N and the variation coefficient thereof is 0.6 or less.
Item 6.
2. An organic piezoelectric film according to item 1, wherein the piezoelectric constant d ₃₃ is in the range of 6.0 to less than 10.0 pC/N and the variation coefficient thereof is 0.4 or less.
Item 7.
2. An organic piezoelectric film according to item 1, wherein the piezoelectric constant d ₃₃ is in the range of 10.0 to less than 14.0 pC/N and the variation coefficient thereof is 0.3 or less.
Item 8.
2. An organic piezoelectric film according to item 1, wherein the piezoelectric constant d ₃₃ is in the range of 14.0 to 30.0 pC/N and the variation coefficient thereof is 0.15 or less.
Item 9.
Item 9. The organic piezoelectric film according to any one of items 1 to 8, having a tensile elastic modulus in the range of 0.4 to 5 GPa.
Item 10.
Item 10. The organic piezoelectric film according to any one of items 1 to 9, wherein the retardation is in the range of 200 to 10,000 nm.
Item 11.
Item 10. The organic piezoelectric film according to any one of items 1 to 9, wherein the retardation is in the range of 0.5 to 200 nm.
Item 12.
Item 12. The organic piezoelectric film according to any one of items 1 to 11, which is made of a polarized vinylidene fluoride polymer film.
Item 13.
Item 13. The organic piezoelectric film according to any one of items 1 to 12, wherein the internal haze value is within a range of 0.05 to 80%.
Item 14.
Item 13. The organic piezoelectric film according to any one of items 1 to 12, wherein the internal haze value is within a range of 5 to 90%.
Item 15.
Item 15. A piezoelectric panel having the organic piezoelectric film according to any one of items 1 to 14 (preferably, the organic piezoelectric film according to any one of items 1 to 13).
Item 16.
Item 15. A pressure sensor comprising the organic piezoelectric film according to any one of items 1 to 14 (preferably the organic piezoelectric film according to any one of items 1 to 12 and 14).
Item 17.
Item 17. A haptic device comprising the organic piezoelectric film according to any one of Items 1 to 14 (preferably the organic piezoelectric film according to any one of Items 1, 2, 5 to 12, and 14). Item 18.
Item 15. A vibration power generating device having the organic piezoelectric film according to any one of items 1 to 14 (preferably, the organic piezoelectric film according to any one of items 1, 2, 5 to 12, and 14).
Item 19.
A flat speaker having the organic piezoelectric film according to any one of items 1 to 14 (preferably, the organic piezoelectric film according to any one of items 1, 2, 5 to 12, and 14).

According to the present invention, there is provided an organic piezoelectric film having small in-plane variation in piezoelectricity.
The organic piezoelectric film of the present invention is excellent in that it is less likely to malfunction when used in, for example, a touch panel capable of detecting touch pressure (particularly when used in a large-area touch panel capable of detecting touch pressure).
Furthermore, the organic piezoelectric film of the present invention is excellent in that stable sensing can be achieved when used in, for example, a pressure sensor (especially when used in a large-area pressure sensor).
Furthermore, the organic piezoelectric film of the present invention is excellent in that, for example, when used in a haptic device, operational errors and malfunctions of the device are unlikely to occur.
Furthermore, the organic piezoelectric film of the present invention is advantageous in that, for example, when used in a vibration power generation device, a constant and stable amount of power can be generated.
Furthermore, the organic piezoelectric film of the present invention is excellent in that, for example, when used in a flat speaker (particularly when used in a large-area flat speaker), high sound quality can be obtained.

FIG. 1 is a schematic diagram showing an overview of a manufacturing apparatus used in manufacturing the organic piezoelectric film of Example 3.

Terms , symbols and abbreviations used herein are to be interpreted in the context of the present specification and in the sense commonly used in the technical field to which the present invention pertains, unless otherwise specified.
As used herein, the phrase "comprising" is intended to encompass the phrases "consisting essentially of" and "consisting of."
In this specification, "detection" of "touch position" refers to determining the touch position, while "detection" of "touch pressure" refers to determining the presence or absence, speed, magnitude, or a combination thereof of pressure.
As used herein, the term "touch" encompasses touching, being touched, pressing, being pressed, and contacting.
As used herein, the term "polarized" means having an electric charge imparted to the surface, i.e., the polarized film can be an electret.
In this specification, the term "haptic device" refers to a device that has the function of providing tactile feedback to a user.
Unless otherwise specified, symbols and abbreviations in this specification should be interpreted in the context of this specification as having the meanings commonly used in the technical field to which the present invention pertains.
As used herein, "variance" is the ratio of standard deviation/arithmetic mean.

Organic Piezoelectric Film The organic piezoelectric film of the present invention is an organic piezoelectric film having a coefficient of variation of the piezoelectric constant _d33 of 2.0 or less.
The organic piezoelectric film of the present invention will be described in detail below.

The organic piezoelectric film of the present invention is a film (polymer film) formed from an organic polymer. Examples of the "organic piezoelectric film" include a polarized vinylidene fluoride polymer film, an odd-chain nylon piezoelectric film, and polylactic acid. The "organic piezoelectric film" may contain components other than the polymer. The "organic piezoelectric film" includes a film made of the polymer and a film in which an inorganic substance is dispersed in the polymer.
The content of the polymer in the organic piezoelectric film of the present invention (i.e., the polymer forming the organic piezoelectric film of the present invention) is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass. The upper limit of the content is not particularly limited, and may be, for example, 100% by mass or 99% by mass.
The polymer is preferably a vinylidene fluoride polymer.
The organic piezoelectric film of the present invention preferably comprises a polarized vinylidene fluoride-based polymer film.
In this specification, examples of the "vinylidene fluoride polymer film" include vinylidene fluoride/tetrafluoroethylene copolymer films, vinylidene fluoride/trifluoroethylene copolymer films, and polyvinylidene fluoride films.
The vinylidene fluoride polymer film is preferably a vinylidene fluoride/tetrafluoroethylene copolymer film.
The "vinylidene fluoride polymer film" may contain additives that are commonly used in resin films.

The "vinylidene fluoride polymer film" is a film composed of a vinylidene fluoride polymer and contains a vinylidene fluoride polymer.

Examples of the "vinylidene fluoride polymer" include:
(1) a copolymer of vinylidene fluoride and one or more monomers copolymerizable therewith; and (2) polyvinylidene fluoride.

Examples of the "monomer copolymerizable therewith" in the "(1) copolymer of vinylidene fluoride and one or more monomers copolymerizable therewith" include trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and vinyl fluoride.
The "one or more monomers copolymerizable therewith" or one of them is preferably tetrafluoroethylene.
A preferred example of the "vinylidene fluoride polymer" is a vinylidene fluoride/tetrafluoroethylene copolymer.
The "vinylidene fluoride/tetrafluoroethylene copolymer" may contain repeating units derived from monomers other than vinylidene fluoride and tetrafluoroethylene, so long as the properties relating to the present invention are not significantly impaired.
The above-mentioned "(1) copolymer of vinylidene fluoride and one or more monomers copolymerizable therewith" contains 50 mol % or more (preferably 60 mol % or more) of repeating units derived from vinylidene fluoride.
The molar ratio of (repeating units derived from tetrafluoroethylene)/(repeating units derived from vinylidene fluoride) in the "vinylidene fluoride/tetrafluoroethylene copolymer" is preferably within the range of 5/95 to 36/64, more preferably within the range of 15/85 to 25/75, and even more preferably within the range of 18/82 to 22/78.

The "vinylidene fluoride/tetrafluoroethylene copolymer" may contain repeating units derived from monomers other than vinylidene fluoride and tetrafluoroethylene, so long as the properties related to the present invention are not significantly impaired. Usually, the content of such repeating units is 10 mol% or less. Such monomers are not limited as long as they are copolymerizable with vinylidene fluoride monomers and tetrafluoroethylene monomers, and examples thereof include:
(1) Fluoromonomers (e.g., vinyl fluoride (VF), trifluoroethylene (TrFE), hexafluoropropene (HFP), 1-chloro-1-fluoro-ethylene (1,1-CFE), 1-chloro-2-fluoro-ethylene (1,2-CFE), 1-chloro-2,2-difluoroethylene (CDFE), chlorotrifluoroethylene (CTFE), trifluorovinyl monomers, 1,1,2-trifluorobutene-4-bromo-1-butene, 1,1,2-trifluorobutene-4-silane-1-butene, (1) perfluoroalkyl vinyl ethers, perfluoromethyl vinyl ether (PMVE), perfluoropropyl vinyl ether (PPVE), perfluoroacrylates, 2,2,2-trifluoroethyl acrylate, 2-(perfluorohexyl)ethyl acrylate); and (2) hydrocarbon monomers (e.g., ethylene, propylene, maleic anhydride, vinyl ethers, vinyl esters, allyl glycidyl ether, acrylic acid monomers, methacrylic acid monomers, vinyl acetate.

A suitable example of the "inorganic material" is inorganic oxide particles. By containing the "inorganic oxide particles," the highly dielectric film of the present invention can have a high dielectric constant. This also makes it possible to significantly improve the volume resistivity while maintaining a high dielectric constant.

A suitable example of the "inorganic material" is inorganic oxide particles. By containing the "inorganic oxide particles", the organic piezoelectric film of the present invention can have a high dielectric constant. Furthermore, the volume resistivity can be significantly improved while maintaining a high dielectric constant. Furthermore, the electrical insulation properties can be improved.

The "inorganic oxide particles" are preferably at least one type selected from the group consisting of the following inorganic oxide particles (B1) to (B3).

[Inorganic oxide particles (B1)] Particles of an inorganic oxide of a metal element of Group 2, 3, 4, 12 or 13 of the periodic table, or composite particles of these inorganic oxides Examples of the metal element include Be, Mg, Ca, Sr, Ba, Y, Ti, Zr, Zn, and Al, etc. Among these, the oxides of Al, Mg, Y, and Zn are preferred because they are versatile, inexpensive, and have high volume resistivity.
Among these, specifically, particles of at least one metal oxide selected from _the group consisting of _Al2O3 , _MgO , _ZrO2 , _Y2O3 , BeO, and _MgO.Al2O3 are preferred because _they have a high volume resistivity.
Among these, Al ₂ O ₃ having a γ-type crystal structure is preferred because it has a large specific surface area and good dispersibility in the “polymer” such as a vinylidene fluoride polymer, particularly in a vinylidene fluoride/tetrafluoroethylene copolymer.

[Inorganic oxide particles (B2)] Inorganic composite oxide particles represented by the formula: M ¹ _a1 M ² _b1 O _c1 (wherein M ¹ is a Group 2 metal element; M ² is a Group 4 metal element; a1 is 0.9 to 1.1; b1 is 0.9 to 1.1; c1 is 2.8 to 3.2; M ¹ and M ² can each be one or more metal elements). As the "Group 4 metal element", for example, Ti and Zr are preferred.
As the "Group 2 metal element", for example, Mg, Ca, Sr, and Ba are preferable.
Among the "inorganic composite oxide particles", specifically, particles of at least one inorganic oxide selected from the group consisting of _BaTiO3 , _SrTiO3 , _CaTiO3 , _MgTiO3 , _BaZrO3 , _SrZrO3 , _CaZrO3 , and _MgZrO3 are preferred because of their high volume resistivity.

[Inorganic oxide particles (B3)] Inorganic oxide composite particles of an oxide of a metal element of Group 2, 3, 4, 12, or 13 of the periodic table, and silicon oxide. The "inorganic oxide particles (B3)" are composite particles of the "inorganic oxide" of the "inorganic oxide particles (B1)" and silicon oxide.
Specific examples of the " _{inorganic oxide particles (B3)" include particles of at least one inorganic oxide selected from the group consisting of 3A12O3.2SiO2 , 2MgO.SiO2 , ZrO2.SiO2 ,} and _MgO.SiO2 .

The "inorganic oxide particles" do not necessarily have to be highly dielectric and can be appropriately selected depending on the application of the organic piezoelectric film of the present invention. For example, the use of one type of versatile and inexpensive metal oxide particles (B1) (particularly Al ₂ O ₃ particles and MgO particles) can improve the volume resistivity. The relative dielectric constant (1 kHz, 25° C.) of these one type of metal oxide particles (B1) is usually less than 100, preferably 10 or less.

As the "inorganic oxide particles", ferroelectric inorganic oxide particles (e.g., inorganic oxide particles (B2) and (B3)) may be used for the purpose of improving the dielectric constant. Inorganic materials constituting the ferroelectric inorganic oxide particles (B2) and (B3) include, but are not limited to, composite metal oxides, their composites, solid solutions, and sol-gel bodies.

The organic piezoelectric film of the present invention can contain the inorganic oxide particles in an amount of preferably 0.01 to 300 parts by mass, more preferably 0.1 to 100 parts by mass, per 100 parts by mass of the polymer. If the content of the inorganic oxide particles is too high, it may be difficult to uniformly disperse the inorganic oxide particles in the polymer, and the electrical insulation (voltage resistance) may decrease. If the content is 300 parts by mass or more, the film may become brittle and the tensile strength may decrease. From this perspective, the upper limit of the content is preferably 200 parts by mass, more preferably 150 parts by mass. If the content is too low, it is difficult to obtain an effect of improving the electrical insulation. From this perspective, the lower limit of the content is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, and even more preferably 1 part by mass. On the other hand, when a high total light transmittance and a low total haze value are required for the organic piezoelectric film of the present invention, the content is preferably smaller, and further, when a particularly high total light transmittance and a low total haze value are required for the organic piezoelectric film of the present invention, the organic piezoelectric film of the present invention may preferably not contain the "inorganic oxide particles." Specific examples of cases in which a high total light transmittance and a low total haze value are required for the organic piezoelectric film of the present invention include cases in which the organic piezoelectric film of the present invention is used in a piezoelectric panel such as a touch panel.

The average primary particle diameter of the "inorganic oxide particles" is preferably small, and so-called nanoparticles having an average primary particle diameter of 1 μm or less are particularly preferred. By uniformly dispersing such inorganic oxide nanoparticles, the electrical insulation of the film can be significantly improved by adding a small amount. The average primary particle diameter is preferably 800 nm or less, more preferably 500 nm or less, and even more preferably 300 nm or less. There is no particular limit to the lower limit of the average primary particle diameter, but in terms of the difficulty of production, the difficulty of uniform dispersion, and the cost, the average primary particle diameter is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 50 nm or more. Here, when a high total light transmittance and a low total haze value are required for the organic piezoelectric film of the present invention, the average primary particle diameter is preferably smaller. The average primary particle diameter of the "inorganic oxide particles" is calculated using a laser diffraction/scattering type particle size distribution measuring device LA-920 (product name) (Horiba, Ltd.) or an equivalent product.

The dielectric constant (25° C., 1 kHz) of the “inorganic oxide particles” is preferably 10 or more. From the viewpoint of increasing the dielectric constant of the piezoelectric film, the dielectric constant is preferably 100 or more, more preferably 300 or more. The upper limit of the dielectric constant is not particularly limited, but is usually about 3000. The dielectric constant (ε) (25° C., 1 kHz) of the “inorganic oxide particles” is a value calculated by measuring the capacitance (C) using an LCR meter and calculating the capacitance, electrode area (S), and thickness (d) of the sintered body according to the formula C=εε ₀ ×S/d (dielectric constant in ε ₀ vacuum).

The organic piezoelectric film of the present invention may contain other components, such as affinity improvers, as necessary.

The "affinity improver" is contained in the organic piezoelectric film of the present invention when the organic piezoelectric film of the present invention contains the "inorganic oxide particles".
The "affinity improver" can increase the affinity between the "inorganic oxide particles" and the "polymer", uniformly disperse the "inorganic oxide particles" in the "polymer", firmly bond the "inorganic oxide particles" and the "polymer" in the film, suppress the generation of voids, and increase the relative dielectric constant.

As the "affinity improver," a coupling agent, a surfactant, or an epoxy group-containing compound is effective.

Examples of the "coupling agent" include organotitanium compounds, organosilane compounds, organozirconium compounds, organoaluminum compounds, and organophosphorus compounds.

Examples of the "organic titanium compound" include coupling agents such as alkoxytitanium, titanium chelate, and titanium acylate. Among them, preferred examples include alkoxytitanium and titanium chelate because of their good affinity with the "inorganic oxide particles."

Specific examples include tetraisopropyl titanate, titanium isopropoxyoctylene glycolate, diisopropoxy bis(acetylacetonato)titanium, diisopropoxy titanium diisostearate, tetraisopropyl bis(dioctylphosphite)titanate, isopropyl tri(n-aminoethyl-aminoethyl)titanate, and tetra(2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl)phosphite titanate.

The "organosilane compound" may be of high molecular weight or low molecular weight, and examples thereof include alkoxysilanes such as monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraalkoxysilane. Vinylsilane, epoxysilane, aminosilane, metachloroxysilane, and mercaptosilane may also be suitably used.

When alkoxysilanes are used, hydrolysis can be used to further improve the volume resistivity (improved electrical insulation), which is an effect of surface treatment.

Examples of the "organic zirconium compound" include alkoxy zirconium and zirconium chelate.

Examples of the "organoaluminum compound" include alkoxyaluminum and aluminum chelate.

Examples of the "organophosphorus compounds" include phosphites, phosphate esters, and phosphate chelates.

The "surfactant" as an affinity improver may be a polymer or a low molecular weight type, and examples thereof include nonionic surfactants, anionic surfactants, and cationic surfactants. Among these, polymer surfactants are preferred because of their good thermal stability.

Examples of the "nonionic surfactant" include polyether derivatives, polyvinylpyrrolidone derivatives, and alcohol derivatives, and among these, polyether derivatives are preferred because of their good affinity with the "inorganic oxide particles."

Examples of the "anionic surfactant" include polymers containing sulfonic acid, carboxylic acid, and salts thereof. Among them, preferred examples include acrylic acid derivative polymers (poly(acrylic acid) derivatives) and methacrylic acid derivative polymers (poly(methacrylic acid) derivatives) because of their good affinity with the "polymer."

Examples of the "cationic surfactant" include amine compounds, compounds having nitrogen-containing composite rings such as imidazoline, and their halide salts.

The "epoxy group-containing compound" as the "affinity improver" may be a low molecular weight compound or a high molecular weight compound, examples of which include epoxy compounds and glycidyl compounds. Among these, a low molecular weight compound having one epoxy group is preferred because of its particularly good affinity with the "polymer."

A preferred example of the "epoxy group-containing compound" is a compound represented by the formula: The compound has excellent affinity with the "polymer".

(wherein R represents a hydrogen atom, a methyl group, a hydrocarbon group having 2 to 10 carbon atoms which may have an oxygen atom or a nitrogen atom interposed therebetween, or an aromatic ring group which may be substituted; l represents 0 or 1; m represents 0 or 1; and n represents an integer of 0 to 10.)

Examples of this include:
Examples of compounds having a ketone group or an ester group include:

The "affinity improver" can be used in an amount that does not impair the effects of the present invention, but specifically, in terms of uniform dispersion and high relative dielectric constant of the resulting film, the amount is preferably in the range of 0.01 to 30 parts by weight, more preferably in the range of 0.1 to 25 parts by weight, and even more preferably in the range of 1 to 20 parts by weight, per 100 parts by weight of the "inorganic oxide particles."

Furthermore, the organic piezoelectric film of the present invention may contain additives other than those mentioned above, as long as the effects of the present invention are not lost.

In this specification, the "piezoelectric constant d ₃₃ " of the organic piezoelectric film is a value determined according to the following measurement method.

Piezoelectric constant and its variation coefficient

<Method of determining piezoelectric constant _d33 >
The piezoelectric constant d ₃₃ is measured using a piezometer system PM300 manufactured by PIEZOTEST (a pin with a tip of 1.5 mm diameter is attached as a sample fixing jig) or an equivalent product. Here, the piezoelectric constant d ₃₃ is measured at 10 points on the film selected without arbitrariness, and the arithmetic average value is taken as the piezoelectric constant d _33. In the present invention, the selection of 10 points on the film without arbitrariness can be performed, for example, by selecting 10 points at 50 mm intervals on a straight line. Here, arbitrariness means the intention to reduce the coefficient of variation described below.
The measured value of the piezoelectric constant _d33 may be a positive or negative value depending on whether the film is measured on the front or back side, but in this specification, the absolute value of the piezoelectric constant _d33 is described.

The coefficient of variation of the "piezoelectric constant d ₃₃ " of an organic piezoelectric film is the ratio of the standard deviation of the "piezoelectric constant d ₃₃ " to the arithmetic mean.

The variation coefficient of the piezoelectric constant _d33 of the organic piezoelectric film of the present invention is 2.0 or less.
As a result, the organic piezoelectric film of the present invention has small in-plane variation in piezoelectricity, and specifically, as a result, for example, the following advantages are obtained.
The organic piezoelectric film of the present invention is unlikely to malfunction, for example, when used in a touch panel capable of detecting touch pressure (particularly when used in a large-area touch panel capable of detecting touch pressure).
Furthermore, when the organic piezoelectric film of the present invention is used in, for example, a pressure sensor (especially when used in a large-area pressure sensor), stable sensing can be achieved.
Furthermore, when the organic piezoelectric film of the present invention is used in, for example, a haptic device, operational errors and malfunctions of the device are unlikely to occur.
Furthermore, when the organic piezoelectric film of the present invention is used in, for example, a vibration power generation device, a constant and stable amount of power generation can be obtained.
Furthermore, the organic piezoelectric film of the present invention is excellent in that, for example, when used in a flat speaker (particularly when used in a large-area flat speaker), high sound quality can be obtained.

From this viewpoint, it is preferable that the coefficient of variation of the piezoelectric constant _d33 of the organic piezoelectric film of the present invention is smaller, and therefore, the upper limit of the coefficient of variation is preferably 1.0, more preferably 0.6, even more preferably 0.4, still more preferably 0.3, and particularly preferably 0.15.

On the other hand, in some applications or usage modes of the organic piezoelectric film of the present invention, it may not be necessary for the coefficient of variation to be very small. In such cases, a larger coefficient of variation may be advantageous in terms of production costs, etc.
Therefore, the lower limit of the coefficient of variation of the piezoelectric constant _d33 of the organic piezoelectric film of the present invention can be, for example, 0.0001, 0.001, 0.01, or 0.02.

The coefficient of variation of the piezoelectric constant d ₃₃ of the organic piezoelectric film can be, for example, in the range of 0.01 to 1.0, in the range of 0.01 to 0.6, in the range of 0.01 to 0.5, in the range of 0.01 to 0.4, or in the range of 0.01 to 0.3.

The preferred piezoelectric constant _d33 of the organic piezoelectric film of the present invention may vary depending on the application or mode of use.
A preferred upper limit for the piezoelectric constant d ₃₃ of the organic piezoelectric film of the present invention can be, for example, 30 pC/N, 28 pC/N, 26 pC/N, or 20 pC/N.
A preferred lower limit of the piezoelectric constant d ₃₃ of the organic piezoelectric film of the present invention can be, for example, 0.5 pC/N, 3 pC/N, 5 pC/N, 7 pC/N, or 9 pC/N.
The piezoelectric constant d ₃₃ of the organic piezoelectric film can be in the range of 0.5 to 30 pC/N, in the range of 0.5 to 28 pC/N, in the range of 0.5 to 26 pC/N, in the range of 0.5 to 20 pC/N, in the range of 3 to 30 pC/N, in the range of 5 to 30 pC/N, in the range of 7 to 30 pC/N, or in the range of 9 to 30 pC/N.

In a preferred embodiment of the present invention (the embodiment of item 3 above), the organic piezoelectric film has a piezoelectric constant d ₃₃ in the range of 0.5 to less than 2.0 pC/N. The variation coefficient of the piezoelectric constant d ₃₃ of the organic piezoelectric film of this embodiment is preferably 1.0 or less, more preferably 0.8 or less, and even more preferably 0.5 or less. The organic piezoelectric film of this embodiment can be suitably used for, for example, a piezoelectric panel or a pressure sensor.

In another preferred embodiment of the present invention (the embodiment of item 4), the organic piezoelectric film has a piezoelectric constant _d33 in the range of 2.0 to less than 4.0 pC/N, and a coefficient of variation of 1.0 or less (preferably 0.8 or less, more preferably 0.5 or less, and even more preferably 0.3 or less). The organic piezoelectric film of this embodiment can be suitably used for, for example, a piezoelectric panel or a pressure sensor.

In another preferred embodiment of the present invention (the embodiment of item 5 above), the organic piezoelectric film has a piezoelectric constant _d33 in the range of 4.0 to less than 6.0 pC/N, and a coefficient of variation of 0.6 or less (preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3 or less). The organic piezoelectric film of this embodiment can be suitably used in, for example, a piezoelectric panel, a pressure sensor, a haptic device, a piezoelectric vibration power generation device, or a flat speaker.

In another preferred embodiment of the present invention (the embodiment of item 6 above), the organic piezoelectric film has a piezoelectric constant _d33 in the range of 6.0 to less than 10.0 pC/N, and a coefficient of variation of 0.4 or less (preferably 0.3 or less, more preferably 0.25 or less, and even more preferably 0.2 or less). The organic piezoelectric film of this embodiment can be suitably used in, for example, a piezoelectric panel, a pressure sensor, a haptic device, a piezoelectric vibration power generation device, or a flat speaker.

In another preferred embodiment of the present invention (the embodiment of item 7), the organic piezoelectric film has a piezoelectric constant _d33 in the range of 10.0 to less than 14.0 pC/N, and a coefficient of variation of 0.3 or less (preferably 0.25 or less, more preferably 0.2 or less, and even more preferably 0.15 or less). The organic piezoelectric film of this embodiment can be suitably used in, for example, a piezoelectric panel, a pressure sensor, a haptic device, a piezoelectric vibration power generation device, or a flat speaker.

In another preferred embodiment of the present invention (the embodiment of item 8), the organic piezoelectric film has a piezoelectric constant _d33 in the range of 14.0 to 30.0 pC/N and a coefficient of variation of 0.15 or less (preferably 0.1 or less, more preferably 0.08 or less, and even more preferably 0.07 or less). The organic piezoelectric film of this embodiment can be suitably used in, for example, a piezoelectric panel, a pressure sensor, a haptic device, a piezoelectric vibration power generation device, or a flat speaker.

Total Light Transmittance

<How to determine total light transmittance>
In this specification, the "total light transmittance" is obtained by a light transmittance test based on JIS K-7361 using a haze meter NDH-7000 SP (product name, Nippon Denshoku Industries Co., Ltd.) or an equivalent product.

The preferred total light transmittance of the organic piezoelectric film of the present invention may vary depending on the application or mode of use.
In applications or usage modes requiring high transparency, a higher total light transmittance is required. On the other hand, in applications or usage modes not requiring high total light transmittance, an organic piezoelectric film having a relatively low total light transmittance may be advantageous in terms of production costs.
The upper limit of the total light transmittance of the organic piezoelectric film of the present invention is, for example, 97%, 96%, or 9
It can be 4%.
The lower limit of the total light transmittance of the organic piezoelectric film of the present invention can be, for example, 70%, 80%, or 90%.
The total light transmittance of the organic piezoelectric film of the present invention can be, for example, in the range of 70 to 97%, in the range of 80 to 96%, or in the range of 80 to 94%.

Haze Value

<How to determine haze value>
In this specification, the "total haze value" is a value measured by a haze meter in accordance with JIS K-7136.
Haze (HAZE) using NDH-7000 SP (product name, Nippon Denshoku Industries) or an equivalent product
This is obtained by a turbidity test.
In this specification, the term "inner haze" refers to the total haze value measured by filling a glass cell with water, inserting a film therein, and measuring the haze value.
As used herein, "outer haze" is calculated by subtracting the internal haze from the total haze of the film.

The preferred total haze value of the organic piezoelectric film of the present invention may vary depending on the application or mode of use.
In applications or usage modes requiring high transparency, a lower haze value is required. On the other hand, in applications or usage modes not requiring a low total haze value, an organic piezoelectric film having a relatively high total haze value may be advantageous in terms of production costs.
The upper limit of the total haze value of the organic piezoelectric film of the present invention can be, for example, 90%, 80%, 70%, or 60%.
The lower limit of the total haze value of the organic piezoelectric film of the present invention can be, for example, 0.3%, 0.4%, 0.5%, 5%, 20%, or 40%.
The total haze value of the organic piezoelectric film of the present invention can be, for example, in the range of 0.3 to 80%, in the range of 0.4 to 70%, in the range of 0.5 to 70%, in the range of 0.5 to 60%, or in the range of 0.5 to 50%.

The preferred internal haze value of the organic piezoelectric film of the present invention may vary depending on the application or mode of use.
In applications or usage modes requiring high transparency, a lower internal haze value is required. On the other hand, in applications or usage modes not requiring a low total haze value, an organic piezoelectric film having a relatively high internal haze value may be advantageous in terms of production costs.
The upper limit of the internal haze value of the organic piezoelectric film of the present invention can be, for example, 90%, 80%, 70%, 60%, 50%, or 40%.
The lower limit of the internal haze value of the organic piezoelectric film of the present invention can be, for example, 0.01%, 0.05%, 0.1%, 0.15%, 5%, 10%, or 20%.
The internal haze value of the organic piezoelectric film of the present invention can be, for example, in the range of 0.05 to 80%, in the range of 0.1 to 70%, or in the range of 0.15 to 60%, in the range of 5 to 90%, in the range of 10 to 80%, or in the range of 20 to 70%.

The preferred external haze value of the organic piezoelectric film of the present invention may vary depending on the application or mode of use.
In applications or usage modes requiring high transparency, a lower external haze value is required. On the other hand, in applications or usage modes not requiring a low total haze value, an organic piezoelectric film having a relatively high external haze value may be advantageous in terms of production costs.
Since the external haze value is calculated by subtracting the internal haze value from the total haze value of the film, examples of the external haze value of the organic piezoelectric film of the present invention can be understood from the above examples of the total haze value and the above examples of the internal haze.

Thickness

<How to determine thickness>
In this specification, the thickness of a film is defined as the arithmetic mean value of thicknesses measured at 10 arbitrarily selected points on the film.

The lower limit of the thickness of the organic piezoelectric film of the present invention can be, for example, 0.1 μm, 0.5 μm, 0.8 μm, 1 μm, 3 μm, 6 μm, 9 μm, or 10 μm.
The upper limit of the thickness of the organic piezoelectric film of the present invention can be, for example, 200 μm, 100 μm, 50 μm, 40 μm, or 30 μm.
The thickness of the organic piezoelectric film of the present invention is, for example, in the range of 0.1 to 200 μm, in the range of 1 to 100 μm, in the range of 0.5 to 100 μm, in the range of 0.8 to 50 μm, in the range of 0.8 to 40 μm, in the range of 3 to 100 μm, in the range of 3 to 50 μm, in the range of 6 to 50 μm, in the range of 9 to 40 μm, in the range of 10 to 50 μm, in the range of 10 to 40 μm, or in the range of 10 to 50 μm.
The preferred thickness may vary depending on the application of the organic piezoelectric film of the present invention.

The organic piezoelectric film of the present invention can be a stretched or unstretched piezoelectric film.
The organic piezoelectric film of the present invention is preferably a non-stretched piezoelectric film.
In relation to this, the organic piezoelectric film of the present invention has high uniformity in thickness. Specifically, it is preferable that the organic piezoelectric film of the present invention has a coefficient of variation in thickness of 10% or less. Here, the coefficient of variation in thickness is the ratio of the standard deviation to the arithmetic mean of the thickness of the film, which is the arithmetic mean value.
In this regard, the organic piezoelectric film of the present invention also has high uniformity in shape and visual uniformity (i.e., less wrinkling and sagging (curvature in the absence of tension other than that due to gravity)).
In relation to this, the organic piezoelectric film of the present invention has a high degree of uniformity in polarizability.

The organic piezoelectric film of the present invention is preferably a non-stretched piezoelectric film.
In relation to this, the organic piezoelectric film of the present invention has a high uniformity in thickness. Specifically, preferably, the organic piezoelectric film of the present invention has a coefficient of variation in thickness of 10% or less. Here, the thickness is measured at 5 mm intervals (i.e., at lattice points of a 5 mm x 5 mm square lattice) over the entire plane of the film, and the arithmetic average value is taken as the thickness of the organic piezoelectric film of the present invention. The coefficient of variation in thickness of the organic piezoelectric film is the ratio of the standard deviation to the arithmetic average of the thickness.
In this regard, the organic piezoelectric film of the present invention also has high uniformity in shape and visual uniformity (i.e., less wrinkling and sagging (curvature in the absence of tension other than that due to gravity)).
In relation to this, the organic piezoelectric film of the present invention has a high degree of uniformity in polarizability.

Tensile modulus of elasticity

<Method of determining tensile modulus of elasticity>
In this specification, the tensile modulus of elasticity is measured by cutting a film sample into a size of 20 mm in width and 100 mm in length, and measuring the elasticity of the film using an autograph (Shimadzu Corporation) under the conditions of a chuck distance of 50 mm and a speed of 50 mm/min.
It is determined by measuring according to IS K7127.

The lower limit of the tensile elastic modulus of the organic piezoelectric film of the present invention can be, for example, 0.4 GPa, 0.5 GPa, or 0.6%.
The upper limit of the tensile elastic modulus of the organic piezoelectric film of the present invention can be, for example, 5 GPa, 4 GPa, or 3 GPa.
The tensile modulus of the organic piezoelectric film of the present invention can be, for example, in the range of 0.5 to 10,000 nm, in the range of 0.5 to 7,000 nm, or in the range of 0.5 to 4,000 nm.

Retardation

<How to determine retardation>
In this specification, the retardation is determined by cutting a film sample into a size of 2 cm x 2 cm or more and measuring it using a retardation film/optical material inspection device RETS-100 (product name, Otsuka Electronics) or an equivalent product. In this specification, the retardation value is the value at 550 nm.

The lower limit of the retardation of the organic piezoelectric film of the present invention is not particularly limited, but can be, for example, 0.5 nm.
The upper limit of the retardation of the organic piezoelectric film of the present invention can be, for example, 10,000 nm, 7,000 nm, or 4,000 nm.
The retardation of the organic piezoelectric film of the present invention may be preferably in the range of 0.5 to 10,000 nm, more preferably in the range of 0.5 to 7,000 nm, and even more preferably in the range of 0.5 to 4,000 nm.
The organic piezoelectric film in a preferred embodiment of the present invention is a stretched film, and has a retardation in the range of 200 to 10,000 nm.
In another preferred embodiment of the present invention, the organic piezoelectric film is a non-stretched film and has a retardation in the range of 0.5 to 200 nm.

Manufacturing Method The organic piezoelectric film of the present invention can be manufactured, for example, by
Step A is to prepare a non-stretched and non-polarized polymer film (e.g., a non-polarized vinylidene fluoride polymer film) by a casting method;
A step B of polarizing the unstretched and unpolarized polymer film; and a step C of heat-treating the unstretched polymer film at any time relative to the step B.
The composition can be produced by a production method including the steps of:

Step A (film preparation step)

The method for producing the "unstretched and non-polarized film" by the casting method includes, for example, (1) a step of dissolving or dispersing the polymer (i.e., the polymer that forms the organic piezoelectric film of the present invention) (e.g., a vinylidene fluoride-based polymer) and the optional components (e.g., inorganic oxide particles and an affinity improver) in a solvent to prepare a liquid composition;
(2) a step of casting (coating) the liquid composition on a substrate; and (3) a step of evaporating the solvent by heating and drying to form a film.

The dissolution temperature in the preparation of the liquid composition is not particularly limited, but a higher dissolution temperature is preferable because it can promote dissolution. However, if the dissolution temperature is too high, the resulting film tends to be colored, so the dissolution temperature is preferably from room temperature to 80° C.
In order to prevent such coloration, preferred examples of the solvent include ketone-based solvents (e.g., methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetone, diethyl ketone, dipropyl ketone, cyclohexanone), ester-based solvents (e.g., ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl lactate), ether-based solvents (e.g., tetrahydrofuran, methyltetrahydrofuran, dioxane), and amide-based solvents (e.g., dimethylformamide (DMF), dimethylacetamide). These solvents may be used alone or in combination of two or more. As the solvent, an amide-based solvent, which is a solvent commonly used to dissolve polyvinylidene fluoride (PVDF), may be used, but the content of the amide-based solvent in the solvent is desirably 50% by weight or less.

The liquid composition may be cast (applied) onto a substrate by a conventional method such as knife coating, cast coating, roll coating, gravure coating, blade coating, rod coating, air doctor coating, or slot die. Among these, the gravure coating or slot die method is preferred because of ease of operation, small variation in the thickness of the resulting film, and excellent productivity. For example, a polyethylene terephthalate (PET) film can be used as the substrate.

The evaporation of the solvent by heat drying may be carried out in accordance with a heat drying method for forming a normal film. The heat drying may be preferably carried out, for example, by passing the liquid composition applied on the substrate through a drying oven in a roll-to-roll manner. Alternatively, the film may be formed by heat drying in a batch manner.
The drying temperature varies depending on the type of polymer constituting the organic piezoelectric film of the present invention. Specifically, for example, when the polymer is a vinylidene fluoride/tetrafluoroethylene copolymer, the drying temperature is preferably within a range of 20° C. to 200° C., more preferably within a range of 60° C. to 190° C., and even more preferably within a range of 80° C. to 190° C.

The thickness of the non-polarized film prepared in step A can be set according to the piezoelectric film to be obtained.

Step B (polarization treatment step)
In step B, the non-polarized film is subjected to a polarization treatment.

The non-polarized copolymer film (hereinafter, sometimes simply referred to as a "non-polarized film") used in step B is preferably not stretched. Also, preferably, in the method for producing an organic piezoelectric film of the present invention, the non-polarized film is not stretched.
The organic piezoelectric film thus obtained has high piezoelectricity even after exposure to high temperatures, and also has a small variation in thickness.

The polarization treatment in step B can be carried out by a conventional method such as corona discharge treatment.

The polarization treatment in step B is preferably carried out by corona discharge.
Either negative or positive corona may be used for the corona discharge, but it is preferable to use negative corona from the viewpoint of ease of polarization of the non-polarized resin film.

The corona discharge treatment is not particularly limited, but can be performed, for example, by applying a voltage to a non-polarized film using a linear electrode as described in JP 2011-181748 A; applying a voltage to a non-polarized film using a needle electrode; or applying a voltage to a non-polarized film using a grid electrode.
The conditions of the corona discharge treatment may be appropriately set based on common knowledge in the technical field to which the present invention pertains. If the conditions of the corona discharge treatment are too weak, the piezoelectricity of the resulting piezoelectric film may be insufficient, whereas if the conditions of the corona discharge treatment are too strong, the resulting piezoelectric film may have point defects.
Here, in order to suppress the in-plane variation of the piezoelectric constant _d33 of the obtained polarized film, it is desirable that the distance between each needle-like electrode and/or linear electrode and the film is constant, that is, that there is no (or very small) in-plane variation in the distance between the electrodes and the film (specifically, the difference between the longest distance and the shortest distance is preferably within 6 mm, more preferably 4 mm, and even more preferably 3 mm).
In order to suppress the in-plane variation of the piezoelectric constant _d33 of the obtained polarized film, for example, when continuous application is performed by roll-to-roll, it is desirable to apply a certain tension to the film and to make the film adhere appropriately and uniformly to the roll.
For example, when continuous application is performed in a roll-to-roll manner using linear electrodes, the DC electric field is, for example, −15 to −25 kV, although it varies depending on the distance between the linear electrodes and the non-polarized film, the film thickness, etc. The treatment speed is, for example, 10 to 500 cm/min.
Alternatively, the polarization treatment may be performed by, for example, sandwiching the non-polarized film between flat electrodes and applying a voltage to the film, in addition to corona discharge. Specifically, when applying a voltage to the non-polarized film by sandwiching the film between flat electrodes, a DC electric field of 0 to 400 MV/m (preferably 50 to 400 MV/m) and an application time of 0.1 seconds to 60 minutes can be used.

Step C (heat treatment step)
Step C is carried out at any time relative to step B. That is, step C can be carried out before, simultaneously with, or after step B. When step C is carried out after step B, the heat treatment of step C can be carried out on the polarized film obtained in step B or on the portion where polarization has been completed in step B. That is, while the polarization treatment of step B is being carried out, the heat treatment of step C may be carried out on the portion where polarization treatment has been completed.
The heat treatment method is not particularly limited, but may be, for example, sandwiching the unstretched polymer film (hereinafter sometimes simply referred to as the film) between two metal plates and heating the metal plates; heating a roll of the film in a thermostatic chamber; or, in the production of the film by a roll-to-roll method, heating a metal roll and bringing the film into contact with the heated metal roll; or passing the film through a heated furnace in a roll-to-roll manner. Here, when step C is performed after step B, the polarized film may be heat-treated alone, or may be layered on another film or metal foil to create a laminated film, which may then be heat-treated. In particular, when heat-treating at high temperatures, the latter method is preferred because it is less likely to cause wrinkles in the polarized film.
The temperature of the heat treatment may vary depending on the type of polarized film being heat treated, but is preferably within the range of (melting point of the polarized film being heat treated - 100) °C to (melting point of the polarized film being heat treated + 40) °C.
Specifically, the temperature of the heat treatment is preferably 80° C. or higher, more preferably 85° C. or higher, and further preferably 90° C. or higher.
The temperature of the heat treatment is preferably 170° C. or less, more preferably 160° C. or less, and further preferably 140° C. or less.
The time for the heat treatment is usually 10 seconds or more, preferably 0.5 minutes or more, more preferably 1 minute or more, and further preferably 2 minutes or more.
Although there is no upper limit to the time for the heat treatment, the time for the heat treatment is usually 60 minutes or less.
The heat treatment is preferably performed at 90° C. or higher for 1 minute or longer.

After the heat treatment, the film is cooled to a predetermined temperature. The temperature is preferably in the range of 0°C to 60°C, and can be room temperature. The cooling rate can be slow or rapid, with rapid cooling being preferred from the viewpoint of productivity. Rapid cooling can be performed, for example, by blowing air. In this specification, such heat treatment of the film may be referred to as annealing treatment.

Rolls of Organic Piezoelectric Film The organic piezoelectric film of the present invention is preferably stored and shipped as a roll.
From the viewpoint of suppressing the occurrence of wrinkles when the organic piezoelectric film of the present invention is formed into such a roll, the elastic modulus is preferably 500 MPa or more. The elastic modulus can be adjusted by selecting the material of the film, etc.
The roll of the organic piezoelectric film of the present invention may consist only of the organic piezoelectric film of the present invention, or may be in a form in which the organic piezoelectric film of the present invention is laminated with a protective film or the like and wound up, or may include a core such as a paper tube, and the organic piezoelectric film of the present invention wound around the core.
A roll of the organic piezoelectric film of the present invention preferably has a width of 50 mm or more and a length of 20 m or more.
A roll of the organic piezoelectric film of the present invention can be prepared, for example, by winding the organic piezoelectric film of the present invention around an unwind roller and a take-up roller.
Here, from the viewpoint of suppressing deflection of the film, it is preferable to make the unwinding roller and the take-up roller parallel to each other, as is usually done.
From the viewpoint of suppressing deflection of the film, among the organic piezoelectric films of the present invention, a film having an elastic modulus of 500 MPa or more may be used.
As the roller, in order to improve the slipperiness of the film of the present invention, it is preferable to use a roller with good slipperiness, specifically a roller covered with a fluororesin, a plated roller, or a roller coated with a release agent.
Here, if the thickness of the film is not uniform, unevenness in the thickness of the roll such as so-called roll edge (high edge; the ends are thicker than the center in the axial direction of the roll; when the film thickness is thinner at both ends than at the center, both ends are recessed compared to the center; or when the thickness changes gradually from one end to the other end, the end with the thinner film is recessed) occurs, which can cause wrinkles. This can also cause the film to sag when unwound (curving when no tension other than that due to gravity is applied).
Generally, in order to prevent the formation of raised edges on a roll, the ends of the film that form the ends of the roll are slit using a slitter, but if the unevenness in the film thickness extends over a wide area from the end of the film, it is difficult to prevent raised edges and dents on the roll by slitting alone.
Generally, the wider the film (eg, 100 mm or more) and the longer the film (eg, 50 m or more), the more likely the raised edges, dents and warping will occur.
However, since the organic piezoelectric film of the present invention has a high degree of thickness uniformity, it is possible to form a roll in which the above-mentioned raised edges, dents, and deflection are suppressed, even when the film is wide (e.g., 100 mm or more) and long (e.g., 50 m or more), either as is or by simply slittering (slitting) the film ends that will become the ends of the roll.
The edges (film ends) removed by the slits can be collected and recycled as the raw material for the organic piezoelectric film of the present invention.
The roll of organic piezoelectric film of the present invention has a high degree of uniformity in thickness, and preferably the ratio of the thickness at the thicker end of the roll to the thickness at the center in the axial direction is within the range of 70 to 130%.
As a result, the deflection of the film when unwound from the roll of the organic piezoelectric film of the present invention is suppressed.

The surface roughness Ra of the roller used in the manufacture of the organic piezoelectric film of the present invention and the roll thereof is preferably 1 μm or less.
This is the "arithmetic mean height" as defined in JIS B 0601:2001.
In addition, it is preferable that at least the surface of the roller used in producing the organic piezoelectric film and roll thereof of the present invention is made of polytetrafluoroethylene (PTFE), chrome plating, or stainless steel (SUS).
These factors can suppress wrinkling of the film.

Applications The organic piezoelectric film of the present invention has high piezoelectricity even after exposure to high temperatures, and therefore can be suitably used in various applications requiring high piezoelectricity and in which there is a possibility of exposure to high temperatures.
Furthermore, the organic piezoelectric film of the present invention has flexibility and can be suitably used for various applications.

Piezoelectric Panel The organic piezoelectric film of the present invention (preferably the organic piezoelectric film according to any one of the embodiments described in items 1 to 13) can be used for a piezoelectric panel (eg, a touch panel capable of detecting touch pressure) or the like.
A touch panel having the organic piezoelectric film of the present invention can detect both a touch position and a touch pressure, and the touch pressure detection performance is not easily deteriorated even after exposure to high temperatures.
The organic piezoelectric film of the present invention can be used in touch panels of any type, such as resistive type and capacitive type.
When used in a touch panel, the organic piezoelectric film of the present invention does not necessarily have to be used for detecting both the touch position and the touch pressure, and the organic piezoelectric film of the present invention may be used for detecting either the touch position or the touch pressure.
The piezoelectric panel having the organic piezoelectric film of the present invention preferably has
A first electrode;
The organic piezoelectric film of the present invention;
a second electrode);
in this order.
The first electrode is disposed directly or indirectly on one main surface of the organic piezoelectric film of the present invention, and the second electrode is disposed directly or indirectly on the other main surface of the organic piezoelectric film of the present invention.
Here, the number of organic piezoelectric films that the piezoelectric panel has can be one or more. Here, in order to eliminate pyroelectric noise of the piezoelectric panel, the two organic piezoelectric films may form a bimorph structure (e.g., a bimorph structure as described in FIG. 18 of WO 2015/053343). At this time, the two organic piezoelectric films may be bonded together with a transparent adhesive or transparent bonding agent. Here, the thickness of the transparent adhesive or transparent bonding agent layer is preferably thicker when its tensile modulus is greater than that of the organic piezoelectric film, and is preferably thinner when its tensile modulus is smaller. In addition, it is preferable that the thickness of the two organic piezoelectric films is thicker on the side to which pressure is applied.
Examples of such electrodes include ITO (indium tin oxide) electrodes, tin oxide electrodes, metal nanowires, metal nanoparticles, and organic conductive resins.

Pressure Sensor The organic piezoelectric film of the present invention (preferably the organic piezoelectric film according to any one of the embodiments described in items 1 to 12 and 14) can be used for a pressure sensor.
The pressure sensor having the organic piezoelectric film of the present invention preferably comprises:
A first electrode;
The organic piezoelectric film of the present invention;
a second electrode);
in this order.
The first electrode is disposed directly or indirectly on one main surface of the organic piezoelectric film of the present invention, and the second electrode is disposed directly or indirectly on the other main surface of the organic piezoelectric film of the present invention.
Examples of such electrodes include ITO (indium tin oxide) electrodes, tin oxide electrodes, metal nanowires, metal nanoparticles, and organic conductive resins.

Haptic Device The organic piezoelectric film of the present invention (preferably the organic piezoelectric film according to any one of the embodiments described in items 1, 2, 5 to 12, and 14) can be suitably used in a haptic device.
The haptic device having the organic piezoelectric film of the present invention preferably comprises:
A first electrode,
It comprises, in this order, an organic piezoelectric film of the present invention, and a second electrode.
The first electrode is disposed directly or indirectly on one main surface of the organic piezoelectric film of the present invention, and the second electrode is disposed directly or indirectly on the other main surface of the organic piezoelectric film of the present invention.
In the haptic device, the organic piezoelectric film of the present invention can convert electrical energy received via the first electrode and the second electrode into mechanical energy, which causes the organic piezoelectric film of the present invention to deform and vibrate, thereby providing tactile feedback to the user.

Piezoelectric Vibration Power Generator The organic piezoelectric film of the present invention (preferably the organic piezoelectric film according to any one of the above items 1, 2, 5 to 12, and 14) can be suitably used in a piezoelectric vibration power generator.
The piezoelectric vibration power generation device having the organic piezoelectric film of the present invention is preferably
Preferably,
A first electrode,
It comprises, in this order, an organic piezoelectric film of the present invention, and a second electrode.
The first electrode is disposed directly or indirectly on one main surface of the organic piezoelectric film of the present invention, and the second electrode is disposed directly or indirectly on the other main surface of the organic piezoelectric film of the present invention.
The organic piezoelectric film of the present invention can convert mechanical energy of vibration received by a piezoelectric vibration power generation device into electrical energy. The electrical energy is sent to a secondary battery or the like via the first electrode and the second electrode.

Flat Speaker The organic piezoelectric film of the present invention can be suitably used in a flat speaker.
The flat speaker having the organic piezoelectric film of the present invention preferably has:
Preferably,
A first electrode,
It comprises, in this order, an organic piezoelectric film of the present invention, and a second electrode.
In the flat speaker, the organic piezoelectric film of the present invention can convert electrical energy received via the first electrode and the second electrode into mechanical energy, which causes the organic piezoelectric film of the present invention to deform and vibrate, thereby generating sound.

A touch panel having the organic piezoelectric film of the present invention can be used in an input device (i.e., an input device having the organic piezoelectric film of the present invention). An input device having the touch panel is capable of input based on touch position, touch pressure, or both. An input device having the touch panel can have a position detection unit and a pressure detection unit.

The input device can be used in electronic devices (e.g., mobile phones (e.g., smartphones), personal digital assistants (PDAs), tablet PCs, ATMs, automatic ticket vending machines, and car navigation systems). Electronic devices having the input device can be operated and actuated based on touch position, touch pressure, or both.

Bimorph Piezoelectric Film When the organic piezoelectric film of the present invention is used in a pressure sensor or a haptic device, the organic piezoelectric film of the present invention may have a so-called bimorph structure in which two organic piezoelectric films are bonded together. That is, the present invention also provides the bimorph piezoelectric film. When such a bimorph piezoelectric film is used as a pressure sensor, it is preferable that the bimorph piezoelectric film has a bimorph structure in which two organic piezoelectric films are bonded together so that the polarization directions of the two organic piezoelectric films are opposite to each other, particularly from the viewpoint of removing pyroelectric noise. As a result, the surfaces on which charges of the same polarity are generated by a temperature rise are arranged on the outside, so that a part or all of the pyroelectric signals (pyroelectric noise) generated from each pyroelectric film can be offset. The bimorph piezoelectric film can usually have a rectangular (e.g., rectangular, square) or circular (e.g., elliptical, perfect circular) shape in a plan view. Both sides of the bimorph piezoelectric film (piezoelectric element) (i.e., two organic piezoelectric films of the present invention) can each be provided with a detection electrode.
The two organic piezoelectric films of the present invention may be attached to each other with a pressure-sensitive adhesive sheet or adhesive layer, may be in direct contact with each other, may be heat-sealed to each other, or may be heat-pressed to each other.
The pressure-sensitive adhesive sheet is not particularly limited as long as it allows two organic piezoelectric films of the present invention to be bonded to each other, and may be composed of one or more layers. That is, when the pressure-sensitive adhesive sheet is composed of one layer, the pressure-sensitive adhesive sheet is composed of a pressure-sensitive adhesive layer, and when the pressure-sensitive adhesive sheet is composed of two or more layers, both outer layers are pressure-sensitive adhesive layers. When the pressure-sensitive adhesive sheet is composed of three or more layers, the pressure-sensitive adhesive sheet may have a substrate layer as an inner layer.
The substrate layer in the pressure-sensitive adhesive sheet may be any transparent film, and is preferably, for example, a film of polyimide, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyparaphenylene sulfide, or polyamideimide.
The pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet can be, for example, a layer containing an acrylic pressure-sensitive adhesive as the pressure-sensitive adhesive.
The adhesive forming the adhesive layer can be, for example, an acrylic adhesive.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

In the examples and comparative examples described below, the following electrodes were used.
<Electrodes used>
(1) A needle-shaped electrode bar in which electrode needles (needle electrodes) (R = 0.06 mm; manufactured by Morita Needle Works) are arranged in a row at 10 mm intervals on the center line of a brass rod 20 mm wide (10 mm thick, 500 mm long). (2) A needle-shaped electrode bar in which electrode needles (R = 0.06 mm; manufactured by Morita Needle Works) are arranged in a row at 15 mm intervals, similar to (1). (3) A wire electrode (500 mm long) made of gold-plated tungsten with a diameter of 0.1 mm.

In the examples and comparative examples described later, the total light transmittance, total haze value, and piezoelectric constant d33 were measured by the following methods.
<Total light transmittance>
The haze was measured using a haze meter NDH-7000SP (product name, Nippon Denshoku Industries Co., Ltd.) according to the method described in JIS K-7361.
<Total haze value>
The haze was measured using a haze meter NDH-7000SP (product name, Nippon Denshoku Industries Co., Ltd.) according to the method described in JIS K-7136.
<Internal haze value>
Water was poured into a quartz cell, the film was inserted therein, and measurements were performed using an NDH-7000SP (product name, Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7136.
<Measurement of piezoelectric constant d33>
The piezoelectric constant _d33 was measured using a piezometer system PM300 manufactured by PIEZOTEST Co., Ltd. In the measurement, the sample was clipped with 1 N, and the generated charge was read when a force of 0.25 N and 110 Hz was applied.
<Tensile elastic modulus>
The tensile modulus of elasticity was determined by cutting a film sample into a size of 20 mm wide x 100 mm long and measuring it using an autograph (Shimadzu Corporation) at a chuck distance of 50 mm and a speed of 50 mm/min according to JIS K7127.
<Retardation>
The retardation is determined by cutting a film sample into a size of 2 cm x 2 cm or more and measuring it using a retardation film/optical material inspection device RETS-100 (product name, Otsuka Electronics). In this specification, the retardation value is the value at 550 nm.

Production Example 1 (Production of Non-Polarized Film)
A vinylidene fluoride/tetrafluoroethylene copolymer film (molar ratio 80:20) having a thickness of 40 μm was produced by the following production method.
A dimethylacetamide (DMAc) or methyl ethyl ketone (MEK) solution of vinylidene fluoride-tetrafluoroethylene copolymer (molar ratio 80:20) was cast onto a PET (polyethylene terephthalate) substrate, and the solvent was evaporated at 180° C. to form a film with a thickness of 40 μm.

Example 1
In an ISO class 7 clean room (humidity 60%), as shown in FIG. 1, a vinylidene fluoride/tetrafluoroethylene copolymer film 2 (hereinafter sometimes simply referred to as film 2) having a width of 550 mm, a length of 200 m, and a thickness (20 to 40 μm) shown in Table 1 was placed on a grounded roller 1 (diameter 200 mm, width 800 mm) made of SUS, so as to move along the roller 1 at a wrap angle of 200°, as shown in FIG. 1. As the first electrode E1, a needle-like electrode was placed so that the arrangement of the needle-like electrodes was perpendicular to the surface of the roller 1 (i.e., in the radial direction of the roller 1) and the tip of the needle-like electrode (first electrode E1) was located 10 mm above the film 2. A first high-voltage power source V1 was connected to the first electrode E1. Furthermore, at positions 100 mm and 150 mm away from the needle-like electrode (first electrode E1) in terms of the length of the film 2, a wire electrode (550 mm long) made of gold-plated tungsten and having a diameter of 0.1 mm was placed as the second electrode E2, at positions 20 mm above the film 2. A second high-voltage power supply V2 was connected to each of the second electrodes E2.
A voltage of -10 kV was applied to the needle electrode (first electrode E1) and a voltage of -10 to -15 kV was applied to the linear electrode (second electrode E2), and then the film 2 was moved in the direction of the arrow in Figure 3 at a speed of 96 cm/min, passing under the corona discharge generated from the tip of the needle electrode (first electrode) and the linear electrode (second electrode) following it, and further contacting the film 2 with a grounded metal roll 3 (diameter 70 mm) to remove electricity from the film 2. Thereafter, a slitter was used to remove a width of 0.5 cm from each end of the film 2, and the resulting polarized film was wound up around a cylindrical core with a diameter of 6 inches while sandwiching a PET film between them.
Here, the distance between the needle-shaped electrode (first electrode E1) and the film 2, and the distance between the linear electrode (second electrode E2) and the film 2 were both adjusted to be constant (the difference between the longest and shortest distances between the electrodes and the film was 0 mm), and eight samples (sample numbers 1 to 8) were manufactured.
In addition, the following two samples (sample numbers 9 and 10)
Unlike the above-mentioned sample numbers 1 to 8, the distance between the needle-shaped electrode (first electrode E1) and the film 2 was adjusted to be constant, but on the other hand, adjusting the distance between the linear electrode (second electrode E2) and the film 2 to be constant was omitted. Therefore, one sample (film thickness 40 μm) was manufactured (sample number 9) in a state where the linear electrode was fixed at an angle and the right end was fixed at a position 25 mm above the film 2 and the left end was fixed at a position 15 mm above the film 2 with respect to the traveling direction of the film 2.
Unlike the above-mentioned sample numbers 1 to 8, the distance between the linear electrode (second electrode E2) and the film 2 was adjusted to be constant, but on the other hand, adjusting the distance between the needle-like electrode (first electrode E1) and the film 2 to be constant was omitted, so that one sample (film thickness 20 μm) was manufactured (sample number 10) in a state where the linear electrode was fixed at an angle and the right end was fixed at a position 20 mm above the film 2 and the left end was fixed at a position 10 mm above the film 2 with respect to the direction of film travel.

Test Example 1
The piezoelectricity was measured using a d33 meter PM300 manufactured by Piezo Test (to which a pin with a tip of 1.5 mm diameter was attached as a sample fixing jig). The meter was set under the following conditions: Rng/Mode: VLO/d33, Frequency: 110 Hz, and Dyn Force: 0.25 N. A 102 g weight was placed on the detection part, and after confirming that the St.F of the meter was 1.0 N, the tip of the sample fixing jig was attached to the measurement in the following manner.
(1) The film was cut to a size of 50 mm [machine direction] x 500 mm [width direction].
(2) The piezoelectric film was placed on a flat and clean surface to avoid creases or wrinkles in the film.
(3) Marks were made with a permanent marker at 10 locations at 50 mm intervals across the width.
(4) Place the film on the detection part, taking care not to wrinkle or crease the film, turn the trigger clockwise, and lower the force head until St.F: 1.0 N. At each of the marked points,
Seconds later the value of d33 was read.
The measurement results are shown in Table 1.

Claims (21)

An organic piezoelectric film having a coefficient of variation of piezoelectric constant _d33 of 0.33 or less in a size of 50 mm x 500 mm. 2. The organic piezoelectric film according to claim 1, wherein the piezoelectric constant _d33 in a size of 50 mm×500 mm is within a range of 0.5 to 30 pC/N. 2. The organic piezoelectric film according to claim 1, wherein the piezoelectric constant _d33 in a size of 50 mm×500 mm is in the range of 0.5 to less than 2.0 pC/N. 2. The organic piezoelectric film according to claim 1, wherein the piezoelectric constant _d33 in a size of 50 mm x 500 mm is in the range of 2.0 to less than 4.0 pC/N. 2. The organic piezoelectric film according to claim 1, wherein the piezoelectric constant _d33 in a size of 50 mm x 500 mm is in the range of 4.0 to less than 6.0 pC/N. 2. The organic piezoelectric film according to claim 1, wherein the piezoelectric constant _d33 in a size of 50 mm x 500 mm is in the range of 6.0 to less than 10.0 pC/N. 2. The organic piezoelectric film according to claim 1, wherein the piezoelectric constant d ₃₃ is in the range of 10.0 to less than 14.0 pC/N and the variation coefficient of the piezoelectric constant d ₃₃ is 0.3 or less in a size of 50 mm×500 mm. 2. The organic piezoelectric film according to claim 1, wherein the piezoelectric constant d ₃₃ in a size of 50 mm×500 mm is in the range of 14.0 to 30.0 pC/N, and the variation coefficient of the piezoelectric constant d ₃₃ is 0.15 or less. An organic piezoelectric film according to any one of claims 1 to 8, having a tensile elastic modulus in the range of 0.4 to 5 GPa. An organic piezoelectric film according to any one of claims 1 to 9, having a retardation in the range of 200 to 10,000 nm. An organic piezoelectric film according to any one of claims 1 to 9, having a retardation in the range of 0.5 to 200 nm. The organic piezoelectric film according to any one of claims 1 to 11, which is made of a polarized vinylidene fluoride polymer film. The organic piezoelectric film according to any one of claims 1 to 12, which is a non-stretched film. An organic piezoelectric film according to any one of claims 1 to 13, having an internal haze value in the range of 0.05 to 80%. An organic piezoelectric film according to any one of claims 1 to 13, having an internal haze value in the range of 5 to 90%. The organic piezoelectric film according to any one of claims 1 to 15, which contains a vinylidene fluoride/tetrafluoroethylene copolymer. A piezoelectric panel having the organic piezoelectric film described in any one of claims 1 to 16. A pressure sensor having the organic piezoelectric film according to any one of claims 1 to 16. A haptic device having the organic piezoelectric film described in any one of claims 1 to 16. A vibration power generation device having the organic piezoelectric film described in any one of claims 1 to 16. A flat speaker having the organic piezoelectric film described in any one of claims 1 to 16.